Pacific LampreyEntosphenus tridentatus出会える場所と時期

The Pacific lamprey is an ancient, jawless fish native to the North Pacific and its coastal rivers, including the Columbia River system. Although its elongated body resembles an eel, it belongs to a separate lineage of fishes. Most individuals spend their early years in freshwater, feed and grow at sea, and return to rivers to reproduce. Pacific lamprey are culturally important to many Indigenous peoples of the Columbia Basin, including as a traditional food. Dams, habitat degradation, and other pressures have reduced their abundance and access to spawning grounds.

Size

Adults commonly reach 40–70 cm in length, with some growing to about 85 cm.

Weight

Large adults can weigh about 500 g.

Lifespan

Typically about 5–9 years, although life-cycle length varies.

Status

Least Concern (IUCN); many Columbia Basin populations have declined.

Pacific lamprey are anadromous, migrating between freshwater and the ocean during their life cycle. Larvae, called ammocoetes, spend several years buried in fine river sediments. They then transform into juveniles with functional eyes and a toothed oral disc before migrating downstream. At sea, they attach to other fishes to feed. Returning adults stop feeding and rely on stored energy during their freshwater migration. They often move upstream at night and shelter beneath rocks or in other cover during daylight. Their oral disc helps them grip surfaces while negotiating strong currents and some obstacles, although dams can seriously impede passage. Adults move stones to create shallow spawning nests in gravel and die after reproduction.

• Despite their eel-like appearance, lamprey are jawless fishes, not eels.
• Their skeleton is made of cartilage rather than bone.
• Their sucking mouth serves both as a feeding tool and an anchor in strong currents.
• After spawning, their bodies return ocean-derived nutrients to freshwater ecosystems.

Wildlife opportunities depend on the river reach, water levels and species. River-specific viewing months have not been confirmed; general species seasons are not a local sighting forecast.

Pacific lamprey use both marine and freshwater habitats around the North Pacific. In the Columbia Basin, they occupy the main river and accessible tributaries, with different habitats needed at each life stage. Larvae favor depositional areas with fine sand, silt, and organic material where they can burrow and filter-feed. Spawning takes place in flowing freshwater over gravel and small stones. Connected migration routes, suitable flows, and good water quality are important throughout their freshwater life.

Larvae filter microscopic algae, microorganisms, and fine organic particles from water passing through their burrows. During the marine feeding stage, Pacific lamprey attach to fishes and consume blood and body fluids using their toothed oral disc and rasping tongue. Hosts include salmon and various other marine fishes. Adults returning to freshwater to spawn no longer feed.

Common name

Pacific Lamprey

Scientific name

Entosphenus tridentatus

Animal group

Fish

Size

Adults commonly reach 40–70 cm in length, with some growing to about 85 cm.

Weight

Large adults can weigh about 500 g.

Lifespan

Typically about 5–9 years, although life-cycle length varies.

Status

Least Concern (IUCN); many Columbia Basin populations have declined.

Identification

Adults have a long, smooth, scaleless body, no paired fins, and a round sucking mouth instead of jaws. Look for seven small gill openings in a row on each side behind the eye. Color ranges from bluish gray or brown above to a paler underside, with returning adults often appearing less silvery than marine fish. Three prominent teeth above the mouth opening are characteristic, but distinguishing Pacific lamprey from other lamprey species usually requires close examination rather than a distant view.